Julia. Julia / Julialang is so pedantically tested and the names are pretty meticulously chosen. The algorithms in Base are almost all generic and handle a very wide variety of inputs without catering to them. If you want to learn Julia, along with good software engineering, looking at the Base library is quite recommended.
Julia requires patched versions of things like LLVM in order for all tests to pass because upstreaming bugfixes take time. This has given some Linux package managers an issue since they try to build using system LLVM/OpenBLAS/etc. with the known bugs. I agree this does cause some distribution problems, but as a scientist and mathematician I do like that the standard distribution of Julia uses the most numerically correct versions (as of current knowledge) of the dependencies as it can, and has a test to identify known potential issues. To me this is good practice.
But anyways, I was talking about the Julia Base library and its numerical routines. I just look at the Julia code and don't touch the build systems.
